Active Vs. Passive SUB

[bilgirami]

Hey guys, can someone explain the differnce between active and passive subwoofer. I know some subs have both an active and a passive sub. I am not very clar on the difference.
Thanks

 

[Captainmorgan89]

Passive = No power Amp built in, they use an external amp. Hope it helps!

 

[bilgirami]

Passive = No power Amp built in, they use an external amp. Hope it helps!

That was was easy.
So whats the deal with subs that have an active and a passive driver. Is an eternal amp needed for the passive driver in this case?

 

[fmw]

That was was easy.
So whats the deal with subs that have an active and a passive driver. Is an eternal amp needed for the passive driver in this case?

A passive radiator is a speaker without a motor (voice coil.) Instead of being driven by an electric current and a voice coil, it is driven by the change of pressure in the enclosure. It isn't a driver at all. It can enhance the bass volume, however.

 

[markw]

All "drivers" are passive.

A "driver" is just the bare speaker itself, no box, no crossover, no nothing.

A simple subwoofer driver, all alone in a box with nothing else, is a passive subwoofer. To use this with an AVR's LFE (or subwoofer) line-level output you need a power amp.

Put a power amp and perhaps a crossover in that box and you have a powered subwoofer.

 

[Exit]

A passive radiator functions like a port in a subwoofer in that it is powered by the acoustic energy generated off the rear of the main driver as it moves in and out. The sound generated by the passive radiator or the port is omni-directional low frequency output which combines with the output from the main driver and usually is tuned to extend the low frequency response. This design has traditionally been referred to as a “bass reflex” design and typically, with all other things equal, has a higher acoustic output than sealed designs. Sealed design subwoofers that have no ports or passive radiators are referred to as an “acoustic suspension” design. Some feel that these designs are more accurate and “musical” than bass reflex designs, but the accuracy and “musicality” of a subwoofer depend more on its design and construction than on the type of subwoofer. There are examples of excellent and poor designs in both categories.

 

[Seth=L]

Sunfire and Def Tech come to mind when I think of subwoofers with passive radiators (the more appropriate term for what the OP was calling a passive driver as drivers indicate magnet structure and voice coils). One driver is driven like any normal active subwoofer, the passive radiator is essentially a bass vent that doesn't allow air to escape from the cabinet. The advantages of this configuration are that the subwoofer can be made smaller than a ported or sealed subwoofer designed to meet the same output and extention as well as reduced to elluminated noise from bass radiation. The dissadvantages are the subwoofers are hard to place in a room and often have tubby or floppy bass. They also require high headroom amplifiers to reach the same levels of output as their ported and sealed counterparts do. Cost for performance on such subwoofers is typically not as good as ported designs.